timekeeping: Increase granularity of read_persistent_clock()

The persistent clock of some architectures (e.g. s390) have a
better granularity than seconds. To reduce the delta between the
host clock and the guest clock in a virtualized system change the 
read_persistent_clock function to return a struct timespec.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134811.013873340@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index eae4511ceeac..ad63f30fe3da 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -769,7 +769,7 @@ int update_persistent_clock(struct timespec now)
         return ppc_md.set_rtc_time(&tm);
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
         struct rtc_time tm;
         static int first = 1;
@@ -787,8 +787,9 @@ unsigned long read_persistent_clock(void)
         if (!ppc_md.get_rtc_time)
                 return 0;
         ppc_md.get_rtc_time(&tm);
-        return mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
-                      tm.tm_hour, tm.tm_min, tm.tm_sec);
+        ts->tv_sec = mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
+                            tm.tm_hour, tm.tm_min, tm.tm_sec);
+        ts->tv_nsec = 0;
 }
 
 /* clocksource code */